I'm having issues with a Moxa 5230 serial device server similar to what you describe. This device is configured, pingable, etc, and using a terminal emulator I have exchanged data between my customer's touchscreen WinXP panel-mounted PC and a laptop (even with a Keyspan USB-serial adapter inline). I am attempting to communicate with a Yokogawa DA100 data acquisition unit. This device came with software called DAQ32, and the touchscreen can communicate with the DA100 via DAQ32 serially and through Keyspan, but not through the Moxa. I installed port monitor software to see what is happening while DAQ32 establishes contact via a known good configuration as well. I have a Labview program that utilizes DARWIN drivers available from NI and Yokogawa, and with a serial connection I can send and receive data through this VI. MAX's VISA interface is able to at least return error codes from the Yokogawa.
When I open MAX with the Moxa inline, I see the virtual COM port created by the Moxa and am able to open a VISA session, but cannot even get an error return from the DA100.
All serial cables have been custom soldered, so I have checked, doublechecked and ohmed out the cable in use in the non-working configuration.
One other strange thing I've noticed, even under a working configuration, is that the baud rate I see when I probe the VISA session wire does not match Windows setting, MAX setting, dip switch on the DA100 setting or the value being written to it by the DARWIN Initialize VI used in my VI. But it works, so maybe I should count my blessings.
Any help would be greatly appreciated. I have been grinding away at this comms issue for a solid week, with overtime, and I think I might go crazy or move into the woods and go off the grid.
For example most of the inexpensive USB-232 devices don't support calls like flush, and by default NI-VISA calls flush after every write. If the serial driver returns an error or hangs during the flush this will of course cause your LV application to hang or error out.
I've run into this problem with MOXA converters in the past. Ended up switching to a less "reknowned" supplier.
Yokogawa makes an ethernet communication module I could use instead of the RS-232. But, my company is only using the DA100 and the Moxa to match an existing unit by a different OEM. Of course, that original unit didn't have a touchscreen running LabVIEW (pretty much the only extra they are getting out of us.) So I think I need to go as deep and as dark as it takes to get this to work. Can anyone give any more council? Maybe I'm so lost in the murky depths of serial commands that I've forgotten something really simple.
Maybe Rolf could help me... 🙂
Well, it's taken up so much time now that my boss went to the customer with the issue, and the Moxa is out of the picture now. Off of comms issues, and on to programming 🙂